When a person is charged with a crime and makes his or her first court appearance, the judge advises that individual (although usually along with a courtroom full of other folks) of his or her rights. Additionally, the judge advises the defendants of the possible pleas that they can enter. There are three: guilty, not guilty, and no contest. So, what do these pleas actually mean, and what is the difference between them?
Guilty means that the defendant is admitting to what he/she has been charged with. If a guilty plea is entered, the judge may sentence the defendant immediately, or may order a Pre-Sentence Investigation (PSI) to be completed with the probation office before a sentence is imposed.
Not Guilty means that the defendant is not admitting to what he/she has been charged with. This plea is often entered at the outset of the case, essentially as a placeholder, to allow the defendant to meet with his/her attorney, conduct discovery, engage in plea negotiations, and generally decide how to proceed in the case. Ultimately, if the defendant decides to go to trial, he/she will stand on the not guilty plea, and the judge or jury will decide whether the defendant is guilty or not guilty at trial.
No Contest means that the defendant is neither admitting nor denying the charge. Instead, the defendant is allowing the judge to find him/her guilty and impose a sentence without a trial. I often tell my clients that if you disagree with some of the facts in the police reports, but ultimately wish to accept a plea offer and avoid trial, then a no contest plea is the way to go. Generally speaking, prosecutors and judges don't care whether a defendant enters a guilty or no contest plea, so it doesn't lead to a more severe sentence than a guilty plea.
Innocent is not a plea. People sometimes tell me that they want to plead innocent. What they really mean is that they want to enter a not guilty plea, and proceed to trial because they did not do what they are charged with. If you want to look smart, don't tell the judge or your attorney that you're pleading innocent, say you're pleading not guilty.